Preheat oven to 400 F. Grease 2, 12 cup muffin pans.
In medium bowl, combine flour, sugar, baking powder, allspice and salt.
In large bowl, combine sweet potatoes, bananas, butter, eggs and milk; mix well. Add flour mixture and pecans; mix well.
Divide the batter evenly between the muffin pan cups. Bake until tops spring back when lightly touched, about 20 minutes. Serve warm.